Operation of by-product coke oven plants



No'v. 22, 1932. s, R MILLERv 1,888,465

OPERATION 0F BY-PRODUCT COKE OVEN PLANTS ATTORNEYS NOV. 22, 1932. s, P,MILLER 1,888,465

OPERATION OF BY-PRODGT COKE OVEN PLANTS Filed Oct. 2l. 1927 2Sheets-Sheet 2 INVENTOR ATTORNEYS Patented Nov. 22, 1932 UNITED .STATESPATENT OFFICE STUART PARMELEE MILLER, OF ENGLEWOOD, NEW JERSEY, ASSIGNORTO THE BARRETT COMPANY, OF NEW YORK, N. Y., A CORPORATION OF NEW JERSEYOPERATION OF BY-PRODUCT COKE OVEN PLANTS Application led October 21,1927. Serial No. 227,634.

This invention relates to improvements in the operation of coalcarbonization plants such as by-product coke oven plants. Moreparticularly, the invention relates to an inmproved method of operation,whereby, 1nstead of producing tar as a by-product, the by-productoperation is so conducted as to produce a high yield of merchantableoils and an improved quality of coke.

According to the present invention the hot coal distillation gasescoming from the individual coke ovens or retorts at a high temperature,around 600 to 700 C. or higher, are cooled to a regulated lowertemperature, but a temperature which is nevertheless suliiciently highto retain a large part of the oil constituents in the vapor form, Whileparticles of pitch are carried in suspension, the gases are thensubjected to a cleaning treatment to separate suspended pitch particlestherefrom While leaving a large part of the oils in the form of vapors,the resulting cleaned gases are then subjected to cooling andcondensation to recover therefrom clean, or 'substantially cleanmerchantable oils, and the pitch residue is returned to the coke ovensor retorts in admiXture with coal, with resulting improvement in thecoke produced. The distillation of the pitch in the coke oven or retortresults in some increase in the oil vapor content of the resultinggases, and the increased oil content is largely recovered in the form ofclean directly merchantable oils in the further carrying out of theprocess.

The practice of the process of the present invention enablessubstantially the maximum yield-of oils to be recovered as merchantableoils directly at a coal distillation plant.

In the customary method of operation of a by-product coal distillationplant, the gases are rapidly cooled inthe hydraulic or collector main bythe introduction of ammonia liquor, or ammonia liquor and tar, and the 7greater part of the tar content of the gases is thrown down andrecovered from the collector main or hydraulic main as a heavy tar. Inthe operation of a coke oven, for example, the gases pass from thecollector main through a cross-over main to condensers, Where a lighttar or tarry oil .is condensed from the gases by further cooling. Theheavy tar from the collector main and the light tar or tarry oils fromthe condcnsers are commonly combined and shipped to tar distillationplants and there distilled.

The distillation of tar in ordinary externally heated tar stills resultsin a very considcrable decomposition of oil constituents contained inthe tar, with the result that the oil yield obtained as a result of thedistillation is considerably less than the oil content of the tardistilled. For example, in simple stills of 10,000 gallons capacityWhere successive charges of tar are distilled by the application ofexternal heat to the still, the distillation of the tar to produce apitch of a melting point around 170 F. gives an oil yield of only about33 per cent of the tar distilled; While if the distillation is carriedfurther to produce a pitch having a melting point around 300 F., the oilyield is increased only to about 44 per cent, and coking of the tar maybegin before a pitch of a melting point around 400 F. is reached.

The present invention provides for the production, directly from coaldistillation gases, of either a pitch of medium melting point around 200F., or the production of a relatively hard or high melting point. pitchfrom which most of the oils are excluded, and the return of such pitchto the coke oven or retort. `Such pitch, in admiXt-ure with the coal,gives a high percentage of coke and a low yield of tar constituents. Thetar constituents can be largely recovered as oil constituents, and onlya limited amount of the heavier pitch constituents returned to the cokeoven or retort, in admixture with coal during further operation. As aresult, the pitch contributes to the coke produced a high percentageyield of pitch coke, and only a small increase in tar content of theresulting gases.

The present invention includes improvements in the production andhandling of the pitch which is produced and employed vin the process, asWell as improvements in the coking operation and in the production of animproved coke. The invention also includes the direct production ofmerchantable oil products, particularly clean oils, which may bedirectly sold and employed, for example, as creosote oils, or which maybe employed,

with addition of tai-,a as an improved coal tarA `0 a relatively highmelting point. For eX- ample, by cooling hot coke oven gases to such atemperature that the pitch particles separated therefrom form/a pitchproduct having a meltingpoint around 300 F., the pitch producedrepresents only around one-third or less of the total tar which would berecovered from the gases, while the remaining twothirds of the normaltar content is left in the form of vapors, and can be subsequentlydirectly recovered as clean or relatively clean oils, suitable for use,for example, for creosoting purposes. By subjecting the gases to acleaning treatment at a still iiglier temperature, so as to separatetherefrom a pitch having a melting point around 400 F., the pitchrepresents only around one-fourth or oneifth of the normal tar contentof the gases, and the remaining three-quarters or fourfifths of thenormal tar content is left in the form of vapors or clean oils which canbe `subsequently directly condensed and recovered as merchantable oilproducts, requiring no further distillation.

Where the maximum oil yield is not desired, the pitch produced may havea lower melting point, e. g., around 200 or 250 F. If the temperature istoo high, the pitch may not be sulliciently fiuid to flow from theelectrical precipitator employed for cleaning the gases and separatingthe pitch therefrom, so that, in general, the gases should be cooled toa temperature below that at which pitch will not flow from theapparatus, so as to recover a pitch product in a sufficiently Huidstate. Pitch of a melting point around 300 or 400 F., or even higher,can be directly obtained,

and the proper temperature of the gases can be readily determined andcontrolled by observing the melting point and character of the pitchseparated from the gases at the temperature of cleaning.

Pitch of such high melting point, e. g.,

` around 400 F., gives a high yield of coke,

amounting to around three-quarters or more of the total Weight of thepitch, while it gives only a limited distillation of the pitchconstituents. As a result, it is possible to, add a relatively largeamount of the high melting l point directly recovered pitch to the colteoven charge, and thereby produce a new and superior coke productcontaining a relatively large proportion of pitch coke. Pitch of lowermelting point can readily be produced and employed in the process.

In the operation of the process, the gases coming from the individualcoke ovens or r'etoi-ts may be collected in a common collector orhydraulic main such as is now commonly used in by-product coaldistillation plants, but instead of cooling the gases rapidly toseparate tar therefrom, the gases should be kept hot and the coolingshouid be regulated. This regulation can be accomplished by indirect aircooling of the gases, or by the introduction of a very small amount ofcooling liquid into the gases, which, by evaporation,

will cool the gases to the desired temperature. Ammonia liquor, in verysmall amount, may be employed, in which case some local overcooling ofthe gases may take place with separation of some heavy tar therefrom,but the average temperature of the gases can be kept suliciently high bylimiting and regulating the amount of ammonia liquor to allow collectionof the desired high melting point pitch.

The cleaning of the gases at a high temperature, to separate suspendedpitch particles therefrom. can be effected by scrubbing of the gaseswith pitch of a temperature and composition the same as or similar tothat cariied in suspension in the gases, but it is more advantageouslyeffected with an electrical precipitator which is maintained at theproper temperature, for example, by heavy insulation or even by heatingto prevent cooling of the gases passing through the precipitator.

The temperature at which the gases are subjected to the cleaningtreatment will vary with the melting point of the pitch to be produced,and may vary with different gases for production of pitch of the samemelting point, depending upon the composition of the gases, which, inturn. will vary somewhat with the character of the coal coked. themanner of carrying out the coking operation. whether rapidlypor slowly.and upon the type of oven or retort, etc. For example, with certain cokeoven gases. a pitch of melting point around 290 F. (cube-in-air method)observing the melting point of the pitch separated from them, and byincreasing or decreasing the temperature of the gases to obtain a higheror a lower meltin point pitch.

The pitch will be separated From the coke oven gases in a continuousmanner. The pitch, while still hot and thinly fluid, may be run on tocoal on a conveyor and caused to solidify in contact therewith, but thismethod is not ordinarily one to be recommended. The pitch can be run toa storage place and permitted to solidify and subsequently dug or minedtherefrom after soliditication, but this operation involves unnecessaryhandling of the material.

The pitch which is continuously produced in the practice of theinvention is advantageously continuously treated for the productiontherefrom in a continuous manner of pitch adapted for mixing directlywith the coal. A particularly advantageous method of accomplishing thisis to run the pitch continuously into`a trough into which a. stream ofwater is also directed. The pitch coming into contact with the water issuddenly chilled and broken up into a pulverulent conf dition, which isreadily flushed away with the water to some convenient place of settlingwhere the water can be drained from the pulverulent pitch. The pitch sopulverized is in a condition which enables it to be handled in the samemanner that coal is handled.

Another advantageous method of handling the pitch is to run it ont-o atraveling belt of metal, which is cooled by water sprayed on theunderside to rapidly cool and solidify the pitch. When such a beltpasses yover a pulley, the solidified pitch breaks off and is therebyobtained-in a broken up condition well adapted for handling in admixturewith the coal.

Another advantageous method of handling the pitch is to Hake it on arotating roll. This is accomplished by running the pitch into a panhaving a rotating` hollow metal roll dipping slightly into the pitch inthe pan. The roll is cooled internally. e. g.. by means of Water. Thesurface of the roll as it touches the molten pitch must be warm in orderthat the pitch may adhere to it and be carried up by the roll. This isaccomplished by spraying the cooling water onto the top inner surface ofthe roll at such va rate that the pitch will be suiiciently chilled tobe solid so that it may be scraped off inst before the roll surfacere-enters the molten pitch. The water warmed by the heat in the pitchruns to the lower surface of the roll. The Water is withdrawncontinuously, but a depth of Warm water equal to l to 1/2 the diameterof the roll is allowed to remain atall times in the roll. This maintainsthe lower roll surface at the proper temperature and prevents localover-cooling due to cold water. The pitch scraped from the roll is welladapted for handling and use.

Other methods of converting the hot pitch into a granular or subdividedcondition can be employed, although those above mentioned areparticularly advantageous. The pitch can, for example, be run into atank of water where it will be rapidly cooled and collected in lump andpowder form. It can also be cooled by atomizing or spraying it throughair which may if desired he cooled by the spraying of water therein.

Pitch of high melting point, e. g., around 300 or 4000 F., has manyadvantages when used as part of the charge of the coke ovens. Itsmelting point is so high that it does not soften at any temperature metwith in the handling of the coal preparatory to charging the coke ovens.It can be handled'and stored the same as coal is handled and stored, andbroken up and pulverized in the same way. It can be admiXed in regulatedamounts with the coal before the crushing operation, or it can beseparately crushed and stored in a separate bin.

The proportions in which the hard pitch is admixed with the coal can bevaried. If the pitch is to be mixed with all of the coal charged to allof the coke ovens, and if the pitch available is only that produced atthe coke oven plant, the percentage of pitch admixed with the coal willbe small, amounting usually to less than one per cent of the coalcharged. In such case, the pitch can be admixed with the coal eitherbefore crushing or after crushing, and uniformly mixed with all of thecoal either before it reaches the storage bins from which the individualcoke ovens are charged, or it may be stored in a separate bin and addedto the coal 'in regulated amounts as the coal goes to the pulveri-zer.

Instead of adding the pitch uniformly to all of the ovens, it vcanadvantageously be added in much larger amounts to a limited number ofovens; for example, in amounts representing about ten per cent of thecharge to one-tenth of the ovens of the battery. If a larger amount ofpitch is available from other batteries, the entire battery may beoperated with a larger proportion of the hard pitch added to the coalcharged. With pitch of high melting point, around 300o or 400 F., a veryconsiderable amount of pitch can advantageously be mixed with the coal,for example, around 15 per cent or more of the total charge. I/Vhenpitch of such high melting point is mixed with the coal, the cokeproduced will contain a high percentage of'pitch coke. A new cokeproduct can thus be produced with a pitch colte content of around ten orfifteen per cent or more, and such a new product has advantages forcertain purposes, being a superior metallurgical coke and having a lowerash content than the coke would otherwise have.

The new coke will be lower in ash and lower in sulfur. It will bestronger, will give less braize in handling, will carry a larger burdenin the blast furnace, will have a higher B. t. u. value than coal coke,and will yield less slag. When pitch is used a poorer quality of coalcan be used since the pitch serves as coking constituent, i. e., thebinding agent of coal.

Simultaneously with the production of the hard pitch and its/'return tothe coal charge of the coke ovens, there will be produced cleaned gasesfrom which the clean oils can be directly recovered. For example, whenpitch of melting point around 300 F. is produced, an oil yield around 65to 70 per cent of the tar which would ordinarily be recovered from thegases can be ldirectly obtained by cooling the cleaned gases; while withthe production of pitch having a melting point around 400 F., the oilyield will be around per cent, although the percentage will varysomewhat with diierent coke oven gases and coking practice.

By cooling the cleaned gases there can be directly condensed therefrom atotal oil condensate suitable for use for creosoting purposes. It willcontain a considerable amount of heavy oil constituents, includingconstituents which are grcaselike or resinous or solid in an isolatedstate at ordinary temperature,

but which in admixture with lighter oil constituents, blend therewith toform a homogeneous product. Instead of condensing a total oil from thegases. the gases can be fractionally cooled and different oils separatedtherefrom, particularly a creosote oil which will be a heavy oil, and alighter carbolic or tar acid oil, from which tar acids can be directlyextracted.

The cooling of gases and the recovery of clean oils therefrom can becarried out in condensers of either the indirect or direct type, such asare commonly employed at coke oven bv-product plants. In case heavy taris separated from the gases in the collector main before they go to theelectrical precipitator, this heavv tar may require further handling.

Where the precipitator is arranged on top of the collector main and thepitch is refiuxed back into the main, no heavy tar should be produced ifthe main is at a suiiiciently high temperature. rI`he temperature shouldbe held up to the point at which hi h melting point pitch results. Thiscan e accomplished by allowing accumulation of tar, or pitch, atomizingit and thus keeping main surfaces clean, or by supplying sutiicientpitch to the main to prevent accumulation of too hard pitch in the main.If the collector main is operated with circulation therethrough ofpitch, some pitch may be separated from the gases and added to thecirculating pitch. while some of the oils in the circulating pitch maybe vaporized and increase the vapor content of the gases.

While the cleaning of the coke oven gases at a suiiiciently hightemperature to give a hard pitch of high meltin point presentsadvantages in oil yield an in providing a pitch of low oil content forreturn to the coke ovens, the process can nevertheless be carried outwith many of the advantages hereinbefore described when the gases arecleaned at a lower temperature and when pitch of medium melting point isobtained; for example, pitch of melting point 'around 200 F. or somewhathigher or lower, or pitch of melting point around 225 F. or 250 F. Whenpitches of such melting point are produced from the gases, the oil yieldwill be somewhat lower, but the oil yield will, nevertheless, be muchgreater than the oil yield obtained by thedistillation of tar inordinary externally heated tar stills to produce pitch of similarmelting point.

When such pitch of medium melting point is returned to the coke oven inadmixture with coal, it will be subjected to further distillation duringthe coldng operation. It will,

for the most part be converted into coke, giving, for example, iaroundtwo-thirds of its weight of coke, but it will also'give a considerableamount of oils and tar constituents, which will escape from the cokeoven with the gases produced by the coking of the coal. Some of theconstituents produced from the pitch in the coke oven will be heavyconstituents, but the greater part of the pitch is left behind in thecoke ovens as coke, and since the pitch is subjected to destructivedistillation in the coke oven, the distillates from the pitch will bemade up largely of oils which will be carried in the gases in vaporform. When the coke oven gases from suchoovens are subjected tocleaningwith an electrical precipitator, a considerable part of the oilvapors produced from the pitch in the coke ovens will be left in vaporform and collected with the clean oils from the gases subsequent to thecleaning in the electrical precipitator. The pitch thrown out of thegases in the electrical precipitator will contain only the heaviest ofthe constituents produced by the distillationof the pitch in the cokeovens, and these will be returned to the coke ovens in the furthercarrying out of vthe process.

Accordingly, even with pitches of medium melting point, a high oil yieldis obtained from the cleaned gases, while the pitch is returned to theprocess for the production of coke, additional oils and permanent gases.

The gases from the coke ovens or retorts to which pitch is returned inrelatively large amount may be kept separate from the gases from theother ovens or retorts and separately cleaned with an electricalprecipitator at a high temperature and clean oils subsequently recoveredtherefrom. "In this way oils can be directly produced of somewhatdifferent composition from those obtained from normal coal distillationgases from ovens or retorts to which no pitch is charged with the coal.The cleaning of the gases at a high temperature with an electricalprecipitator gives directly a pitch product which can be readily handledin a hot fluid state and clean oils, and eliminates troubles resultingfrom the handling of tar separated from coal distillation gases Wherepitch in considerable amount is added to the coal charged to the ovensor retorts.

This invention will be further described in connection with theaccompanying drawings, Which illustrate in a somewhat conventional auddiagrammatic manner,`parts of a by-product coke oven plant arranged forthe practice of the invention.

In the accompanying drawings Fig. 1 is a diagrammatic view in elevationWith parts in section, and

Fig. 2 is an enlarged view of part of the apparatus.

In the apparatus illustrated the coke oven 1, has the usual uptakepipes, 2, leading from the individual coke ovens to the collector main3. From the center box 4 of the collector main, a line 5 leads to areceptacle 6 for pitch, or for heavy tar and ammonia liquor, which maycollect in the centerbox during operation. From the collector main 3,the gases lead through a short pipe 7, to an electrical precipitator 8,iny which the gases are subjected to a cleaning treatment at a hightem,- perature.l The cleaned .gases then pass through the cross-overmain 9, to a cooler for creosote oil 10, and then through the line 11,to the' coolers or condensers 12 and 13, shown as direct coolers withWater sprays 141 and 14. The oil condensed in these coolers iscollcctedin decanters 15 and 16, or may be collected in one decanter,from which liquor is drawn off and collected in tank 19. Oil from thedecanter or tank 15, or the total oil, may be returned by line 17,having pump 18 therein, to the creosote condenser 10. The creosote oilcondensed and collected in 10 is run oil' to receptacle 28. From thecondenser 13 the gases pass through line 20 to exhauster 21, and then tothe ammonia absorber or saturator and light oil scrubber (not shown).

From the electrical precipitator 8, the separated pitch runs out throughspout 22 to a trough 23 into which a stream of Water is introduced athigh velocity through pipe 24, with resulting granulation of the hotpitch, which runs down with the Water and is collected in settling basin25. A stream of Water discharged at 45 lbs. gauge pressure through astandard 11/8 inch re nozzle, and on to which the pitch falls, willreadily'granulate 1000 to 2000 gallons of'pitch per hour. After drainageof Water from the pitch it can be handled like coal and conveyed to themixing bins and Withdrawn therefrom in regulated amounts for admixturewith the coal, after which the admixture, suitably disintegrated andmixed together to form a uniform mixture will be stored in the storagebins and charged to the coke ovens as required.

The collector main 3, is shown in F ig. 2 as having spray lines 26 forthe introduction of a limited amount of ammonia liquor, Where this isdesired for regulating the temperature of the gases. 1f a large amountof ammonia liquor is introduced, the gases Will be cooled to too low atemperature, but by using a very small amount of ammonia liquor andproviding only a limited contact of the gases therewith, the average gastemperature of the gases leaving the collector main and going to the.electrical precipitator can be kept sufficiently high even though somelocal overcooling of part of the gases and separation of heavy tartherefrom may take place in the collector main. Only around 131/2 lbs.of Water are required per thousand cubic feet of gas to cool the gas, e.g., from 700o to 300 C. In case a large amount of hot pitch iscirculated through the bottom of the collector main 27, to preventaccumulation of hard pitch therein, the pitch will be drawn oif into thereceptacle 6, and can be further circulated if desired.

In the drawings no insulation is shown, but in practice the electricalprecipitator will be heavily insulated to prevent loss of temperaturetherein, and the connecting pipe 7, leading to the collector main, asWell as the uptake` pipes and the collector main may be provided withthe insulation to prevent excessive lowering of temperature byatmospheric cooling and to permit better regulation of the temperatureby a limited introduction of, for example, ammonia liquor into thecollector main. When a circulating stream of hot pitch is employed inthe collector main atmospheric cooling may be relied up'on to a largeextent, if not-entirely, for cooling of the gases to the desired lowertemperature, While insulation can be employed to prevent too greatcooling.

In the operation of the apparatus described, the pitch will be mixedwith the coal, for example, to the extent of about one or two per centof the charge Where it is admixed with the coal for all of the ovens, orto the extent, for example, of ten per cent 0r more where it is mixedwith the coal for only a limited number of ovens. During the coking ofthe coal the high melting point pitch will also be coked, and there willbe produced a coke product containing pitch coke which may be present toa very considerable extent, e. g., to the extent of ten per cent or moreof the total coke. The coking of the pitch at the same time that thecoal is coked, will result in driving oi' more or less volatileconstituents and decomposition products from the pitch and these willadmix with the distillation gases T e hot gases coming from theindividual coke ovens are collected in the collector main,

and are cooled to a regulated lower temperature which will vary with themelting point of pitch to be produced, but which should not be too high,since the temperature of the gases must be a safe margin below thatwhich would cause carbonizing of pitch deposits on the tubes of theelectrical precipitator. The temrature ofthe gases can readily beregulated y noting the character and melting point of the pitch, andincreasing or decreasing the gas temperature to give pitch oftheydesired melting point, for example, pitch of around 300 F. meltingpoint, or even pitch of around 400 F. melting point. The gases at theregulated temperature are passed through the electrical precipitator,lated or which is heated of temperature so that the gases leave theprecipitator at astemperature the same as or not greatly below that atwhich they enter the precipitator. If the gases are cooled to :anymaterialextent in the precipitator, it ref stilts in furthercondensation of constituents which would otherwise be carried in vaporform with the gases and subsequently recovered as 'part of the cleanoils. If the temperature of the gases passing thru theelectricaprecipitator issuiiiciently high, the suspend articles carriedby the gases and separated t erefrom in the electrical precipitator willgive a pitch of regulated melting point, and will leave the oils,including a largepart of the heavy oils and constituents which in anvisolated state are semi-solid or solid at ordinary temperature as vaporsto be carried along to the condenser.

The pitch thrown down in the electrical precipitator is run into acomminuting device, which in the drawings is a trough supplied withwater to cause the disintegration of the pitch. The hot high meltingpoint lpitchwill be immediately disintegrated`by the cold water comingin contact therewith, and the water will wash the finely divided pitchwith it into a ksuitable collecting receptacle. The comminuted pitch canthen be handled like coal. The excess water can be drained from it andit can then be storedand handled with the same equipment with which coalis handled. Its high melting point prevents any danger of softeningduring handling or storage. Its brittle character makes it readilydisintegrated, so 'that it can be uniformly admixed with the coal.,

The hot cleaned gases from the electrical C precipitator pass first tothe creosote ccn- Which is heavily insup to prevent lowering denser,where they lare cooled in part by indirect cooling, tion of the lighteroils subsequently condensed from thegases. In this way a creosote oilcan be recovered which will be a heavy creo.

sote oil and of particular value for that purpose, because of its heavycharacter. The gases will subsequently be further. cooled to a lowtemperature, e. g., around 250 to C., to condense vthe lighter oils,such as carbolic or tar acid oils, which will be clean oils and can bedirectly extracted for the recovery of tar acids therefrom.

In the drawings the gases from all of the ovens are shown as leading tothe same collector main and to the same common system for handling thegases. In practice it will be understood that a battery of ovens willhave or may have a plurality of collector mains and cross-over mainsleading to the same condensing system or to individual condensingsystems. When a part only of the battery is operated with the additionof the hard pitch to the coal charged to the ovens, the gases from thispart of the battery may be those collected in the same collector main,in which casethe gases may be handled separately from those collected inother collector mains where no pitch is charged with the coal to theovens, and pitch and oils of somewhat diiferent character separatelyrecovered therefrom. Separate collector mains may it desired beinstalled to handle these gases.

The employment of hard pitch, containing, `for example, only around athird to a quarter of its Weight of decomposable volatile constituents,and yielding from two-thirds to threequarters or "more of pitch coke hasthe advantage, among others, that it does not materially increase thetar content of the coal distillation gases, nor decrease the coke yieldfrom'the charge. The hard pitch nevertheless, give on coking oil andpitch con.

during the coking of the mixture in the individual oven or retort. Inthis way all or practically all of the tar content of the gases isconverted into a high yield of valuable oil and coke with someproduction of gas, and without the production of the usual tar whichrequires subsequent distillation. The by-product coke oven can beoperated accordinvly for the production of only clean oils, eche, gas,ammonia and light oils, which are all marketable products, and, inparticular,

and in part by the introducn there isobtained a high yield of valuableloils without the separate production and distillation of tar,;and Vwithgreatly increased yields of oils-'as compared with the yields whichwould be obtained by separate recovery and distillation of tar accordingto ordinary tar distillation methods.

I claim: l

l. The method of producing coke and clean oils from coal which comprisescoking coal in a coke oven, removing entrained-solid pari ticles andentrained liquid particles of high boiling range from the resulting hotfresh distillation gases at a temperature at which the constituents ofthe gas are separated into gases and vapors which pass oi and a pitchresidue which is left behind; returning at least part of the pitch`residue to the oven in admiXture with the coal and coking the mixturetherein, and recovering oils of lower boiling range from the gases andvapors.

- 2. The method of producing coke and clean oils from col whichcomprises coking coal in a coke oven, removing entrained solid andliquid particles from the resulting hot fresh distillation gases at atemperature above the dew point of the tar' oils of lower boilin rangeand at a temperature sufciently hig to form atresidue' comprising mainlypitch, returning at least a part of said pitch residue to the oven' inadmixture with coal and coking the mixture therein, and condensing thegass `from which the said entrained solid andu liquid particles wereseparated to recover oils 'of low boiling range.

In testimony whereof I allix myv signature. STUART PARMELEE MILLER.

